ACI Concrete Strength Testing Technician CP-19 (14)
The capping procedures for concrete cylinders and cores are designed to ensure compliance with
standards for planeness and perpendicularity.
Equipment required for the capping process includes: - Capping plates - Alignment devices - Melting ...
The capping procedures for concrete cylinders and cores are designed to ensure compliance with
standards for planeness and perpendicularity.
Equipment required for the capping process includes:
- Capping plates
- Alignment devices
- Melting pots
The materials used for capping plates, particularly for neat cement and high-strength gypsum plaster,
should be made from glass, metal, granite, or diabase.
Capping sulfur mortar should be formed against metal or stone plates.
The guide bar or bull's eye level's purpose is to ensure caps remain perpendicular to the cylinder's axis
within a tolerance of 0.5 degrees. This statement is True.
To prevent accidents while reheating cooled sulfur, it is recommended to use melting pots that have
peripheral heating.
A stiff layer of neat cement paste should be used to cap fresh concrete cylinders.
Hardened concrete cylinders can be capped with high-strength gypsum paste, neat cement paste, or
sulfur mortar.
It is False that plaster of Paris and mixtures of plaster of Paris and Portland cement qualify as suitable
high-strength plasters.
, Sulfur mortars and high-strength gypsum cement cubes must achieve a minimum compressive strength
of 35 MPa (5000 psi) or correspond to the cylinder strength, whichever is greater.
The cement paste should be applied to freshly molded cylinders between 2 to 4 hours after molding to
allow for the settling of the concrete specimen.
The strength of the paste is influenced by:
a) the water-cement ratio
b) time
d) type of cement
Thus, the correct factors influencing strength are a, b, and d.
When placing the capping plate onto the mound of the paste, a slight twisting motion aids in removing
excess paste and air voids.
Neat cement paste caps are inadvisable for dry specimens, as they may shrink and crack when dry.
Before capping, the technician should ensure that all oily or waxy materials are removed from the ends
of hardened concrete cylinders.
The pot should be emptied and recharged with fresh material at intervals to ensure that no material has
been used more than 5 times.
When capping concrete cylinders with a compressive strength of 35 MPa (5000 psi) or higher, it is False
that one can reuse material from old caps.
To prevent foaming, sulfur mortar must be dry before adding to the pot and should be kept away from
water during heating.
The melting pot for the sulfur mortar must be situated underneath a hood equipped with an exhaust fan
for ventilation.
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